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Unfortunately, we flew to Amsterdam and back to Prague uselessly as a result of the faults on the part of the sales and information chain of air companies and their dealers. We had to pay new holiday and had only 7 days to rest instead of the original 10 days.
Unfortunately, we flew to Amsterdam and then back to Prague uselessly, as a result of a mistake by the airlines and their dealers. We had to pay for a whole new holiday and had only 7 days to rest instead of the original 10 days.
Unfortunately, we flew to Amsterdam and back to Prague uselessly as a result of the faults on the part of the sales and information chain of air companies and their dealers. We had to pay new holiday and had only 7 days to rest instead of the original 10 days.
Thank you very much.
Hanka
I would be inclined to do this:
Unfortunately, as a result of errors on the part of the sales and information departments of the air companies and their agents, we flew to Amsterdam and back to Prague uselessly. We had to pay for a new holiday and had only 7 days in which to rest instead of the 10 days originally intended.
proofreading 
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